The present invention relates to an emulsion of a synthetic resin having improved properties.
Synthetic resin emulsions are useful as adhesives, coating materials, treating agents for fibers and textiles, treating agents for papers, hides and skins, binders for various materials, and modifiers for cement and mortar.
Although processes for the preparation of these synthetic resin emulsions are different somewhat from each other depending on the kinds of resins, the use of an emulsifier or protective colloid is essential in all cases. For instance, emulsions of vinyl resins such as polyvinyl acetate, acrylate polymers and polyvinyl chloride have been prepared by emulsion polymerization of a monomer in the presence of an emulsifier or protective colloid. Also, emulsions of polyester resins, epoxy resins or silicone resins have been prepared by admixing a solution of a resin or a molten resin with an aqueous solution of an emulsifier or protective colloid. Representative emulsifiers or protective colloids are non-ionic surface active agents, anionic surface active agents and water soluble resins, especially polyvinyl alcohol (hereinafter referred to as "PVA"). Since emulsions obtained by using surface active agents lack mechanical stability, PVA has been predominantly used as emulsifiers or protective colloids.
A partially hydrolyzed PVA having an average degree of hydrolysis of about 88% by mole provides emulsions having a large structural viscosity, a small dependency of viscosity stability on temperature change and a good stability in freezing or storage at low temperatures, but the emulsions are lacking in water resistance. On the other hand, in case of using a completely hydrolyzed PVA having an average degree of hydrolysis of about 99% by mole, the obtained emulsions have an excellent water resistance and a small structural viscosity, but are unstable in viscosity depending on temperature change and are poor in freezing stability or storage stability at low temperatures. Therefore, these both types of PVA emulsifiers or protective colloids have been selected in accordance with the uses of emulsions.
In recent years, however, there have been required emulsions having both properties of the partial hydrolysis type PVA and the complete hydrolysis type PVA. That is to say, there have been desired synthetic resin emulsions having an appropriate structural viscosity, a good water resistance, and a viscosity stability, namely a good stability in freezing or storage at low temperatures. In order to obtain such emulsions, it may be considered to combine the partial hydrolysis type PVA and the complete hydrolysis type PVA as an emulsifier or protective colloid. However, in many cases, undesirable properties appear rather than desirable properties from each PVA.
Accordingly, it is an object of the present invention to provide an improved emulsion of a synthetic resin.
A further object of the present invention is to provide a synthetic resin emulsion having both desirable properties of a partial hydrolysis type PVA and a complete hydrolysis type PVA as an emulsifier or protective colloid.
Another object of the present invention is to provide a synthetic resin emulsion suitable for various uses.
These and other objects of the present invention will become apparent from the description hereinafter.